The present invention relates to a flange for connecting pipes, inserting fittings in piping or connecting pipes or fittings to containers and the like.
A variety of flanges are known for removably connecting pipe sections, for installing fittings in piping, for connecting pipes or fittings to containers and the like, and for connecting flanged pipes or covers onto containers and the like. In general the flanges or flanging include a smooth ring of rectangular cross-section (as for example in DE-PS No. 124 715). However, profiled flange rings are also known (as for example in DE-OS No. 20 59 484) of continuous S-shaped cross-section. The flange rings are welded either to a pipe or pipe nozzle or are welded onto the end section of a pipe or pipe nozzle as a welded slip-on flange (as for example in DE-OS No. 21 19 547, FIG. 1). However it is also possible to secure the flange ring on the pipe or pipe nozzle by fixing it against either the raised edge of the end of the pipe or pipe nozzle or a raised edge welded to the end of the pipe or nozzle.
Flange rings are also known which are of U-shaped cross-section. In the apparatus described in DE-GM 71 27 540, the U-shaped profile of the flange ring adds to the strength and stability of the flange, making possible a reduction in the amount of material used. As described in DE-OS 22 36 562, a circular receiving seat of an expansion joint is supported by a U-shaped flange ring with one side of the circular seat being supported on the inner ridge of the U-shaped flange ring and otherwise on the inner edge of the U-shaped flange ring.
A flange joint is constructed with the object of achieving a secure seal of the flange to the connection point while keeping cost as low as possible. In furtherance of this object, high quality material is used where corrosive material comes into contact with the flange joint and lower quality material can be used for other flange joint parts.
Conventional flanges constructed in the above-described manner have not been entirely satisfactory. Since the clamping bolts which are tightened to effect sealing are disposed about the flange spaced radially from the sealing surfaces, the pressing force generated by tightening the clamping bolts develops a bending moment on the flange which brings about an inclined positioning of the sealing surfaces in relation to each other. The sealing or packing which is disposed adjacent to the sealing surface is accordingly deformed in cross section into the shape of a wedge which is thinner at the outer portion of the sealing as a result of higher forces being applied thereat. This occurs in the flange joint disclosed in FR-PS No. 674 447, in which a flange ring of rectangular cross-section bent into a U-shape is disposed at the end of a pipe. The pressing force brought about by tightening the clamping bolts is exerted largely along the outer edge of the U-shaped part of the flange and from there transmitted to the sealing surface, so that the sealing is progressively compacted from the outer edge radially inwardly, resulting in greater compression along the outer portion of the sealing. In DE-GM No. 19 60 147, the sealing is deliberately non-uniformly compressed with the greatest pressure occurring between the inner and outer portions of the sealing.
In the apparatus disclosed in FR-PS No. 647 447 and DE-GM No. 19 60 147, a bending moment set up in the flange ring about its outside edge as the clamping bolts are tightened lifts the inner rim of the flange ring up from the bearing surface at the end of the pipe. To prevent this, a flange connection such as the one disclosed in European Patent No. 79103337 is used. That flange connection comprises an inner rim welded to or on the pipe, pipe nozzle, fitting or container, and an outer rim on a section of the flange disposed radially inwardly from the holes for the clamping bolts but as close as possible thereto which forms the rest and support for the flange ring. The base or flanged area of the outer rim forms the sealing area and an abutment for a flange ring of L-shaped cross section is provided on the inner rim of the ring form part. The abutment supports the inner edge of the flange ring against forces produced by tightening the clamping bolts and prevents an axial movement of the flange ring on the pipe. The apparatus described in this paragraph does not achieve the object described above and does not achieve uniform compression of the sealing.